204 TROPICAL FOEESTS. 



Their average production is perhaps not so great as 

 that of our forest trees, during the short period that 

 they are in activity ; but in all tropical countries the 

 season of growth is double, and in many it is of more 

 frequent occurrence, and where there is humidity 

 enough the growth is constant. The leaves are 

 required for shade ; and as natural circumstances 

 always produce that very organisation or structure 

 which suits them best, the shading leaf is firm in its 

 structure, and not liable to be gnawed and eaten like 

 the more tender ones. 



Woody substance is that which has the tendency 

 to accumulate to excess in those forests ; and, there- 

 fore, the great body of the insects there attack the 

 wood of the trees. As these insects have much 

 labour to perform in clearing the forests of their lum- 

 ber, they exist in proportionate numbers, generally 

 social, and in bands which no man can count. These 

 crowd all parts of the trees, and indeed many of the 

 spaces between them ; but they are on the boles and 

 branches, and in the decaying wood, rather than on 

 the leaves. The winged ones, too, crowd over the 

 trees and the flowers of those climbing plants, with 

 which the boles are entwined and the branches 

 interlaced. These are, however, more seasonal than 

 the races which inhabit the trees, or rear themselves 

 huts and towns on the ground ; and therefore they 

 do not form so large a portion of the food of the more 

 typical scandent birds. The bee-eaters, the cuckoos, 

 some resident and others migrant, and the warblers, 

 and other soft-billed birds which are driven from the 

 temperate climates as the winter sets in, are the chief 

 consumers of this more temporary produce of the 

 tropical forests. 



The same absence of farinaceous seeds which pre- 



